High resolution chromosome analysis should become a valuable tool in the understanding and subclassification of non-Hodgkin's lymphoma. With our present lymph node methotrexate synchronization technique (300-850 band stages) we have found a chromosome defect in 70 of 70 lymphoma patients and 59% of them showed one of five specific chromosome defects. Some of these defects were found to be specific for certain histologic subtypes while others were shared among related disorders. These studies will be continued with an improved synchronization technique which utilizes actinomycin D to obtain mitoses at the 1200 and 2000 band stages. This will enable us to define with more precision the breakpoints involved in the various lymphoma subtypes and possibly uncover subtle rearrangements that have thus far escaped detection. Using this new technique, we also will analyze 12 Burkitt's cell lines with a t(8;14), t(2;14) and t(14;22) translocations, some of which appear to have breakpoints in chromosomes 8 and 24 other than the common ones in subbands 8q24.1 and 14q32.3. This would be of importance to the understanding of the mechanism of c-myc oncogene activation in Burkitt's lymphoma. C-myc maps to band 8q24 and rearranges with the heavy chain immunoglobulin genes of band 14q32; such rearrangement can be contiguous or more than 50 kilobases apart from the C\mu gene.